Characterization of ARC/CL wheat flour, pork meat and skim milk powder reference materials for contents of toxic elements

Summary Wheat flour, pork meat and skim milk powder reference materials (RM) prepared and employed for the activities of the Sub-network on Trace Element Status in Food of the FAO European Cooperative Research Network on Trace Elements were subjected to an interlaboratory comparison study on the contents of Pb, Cd and Hg. The homogeneity of the above materials had earlier been shown to be within 2% for several essential elements and within 5 to 10% for Pb and Cd. An interlaboratory comparison study was conducted involving 17 reference laboratories recognized for their reliability and specialized in heavy metal determinations in biological materials. A total of seven methods based on four different analytical principles were employed to determine the contents of the above heavy metals. After the exclusion of outliers, the recommended concentration values expressed as the medians ±95% confidence limits were established. All of the recommended values reported here fell into category A, i.e. values recommended with a high degree of confidence according to the certification criteria established by Pszonicki. The present materials contain very low naturally occurring levels of all the heavy metals studied and have been successfully employed in the analytical quality control program of the above FAO study during the past five years.     

Anti-Stokes luminescence of europium(III)-doped lanthanum oxychloride

The anti-Stokes luminescence from the ⁵D_1,2,3 levels of Eu³⁺-doped LaOCl was observed at 300 and 77 K under dye-laser excitation to the ⁵D₀ level. A two-photon absorption from the ⁷F₀ ground level to charge-transfer states via the ⁵D₀ level was concluded to be the mechanism involved. The absorption of the first photon through the forbidden ⁵D₀→⁷F₀ transition determines the upconversion efficiency. The two-photon absorption seems to occur as an intra-ion process without interionic energy transfer.     

The transition energy for the polymorphic transformation of CsCl

The transition energy of CsCl for the transformation I ? II has been determined by means of theoretical and experimental methods. The theoretical method was based on a generalized expression of the repulsion energy introduced byWasastjerna and used in his theory of ionic solid solutions [18]. In the present work, the theoretical value of the transition energy, 880±220 cal/mole, is considerably smaller than previous theoretical results and agrees well with our experimental value, 690±28 cal/mole.     

Preparation and testing for homogeneity of spiked strawberry and cabbage candidate reference materials

Strawberry and cabbage candidate reference materials (RMs) have been prepared by our laboratory during 1992–1993. Fresh materials have been homogenized and spiked with known concentrations of pesticides representing compounds commonly used for strawberries and cabbages. The candidate RMs have been then freeze-dried, homogenized, bottled under a stream of nitrogen and stored frozen at –20°C. Homogeneity and stability of the candidate RMs have been studied during the storage period. Homogeneity of the candidate RMs for 5 g samples has been within 10%. Homogeneity and stability studies have been carried out using the conventional multiresidue method of Luke et al. [1]. Instrumental analysis have been performed by gas chromatography mass spectrometry (GC-MS) employing selected ion monitoring (SIM).     

Mobile access to biological databases on the Internet

We have developed a new way of accessing biological databases and bioinformatics applications on the Internet. This new service, bioinformatics wireless application protocol (BioWAP) service, which is accessible by mobile devices makes it possible to access bioinformatics services, where normal PC or personal digital assistant (PDA) connections are not feasible. The BioWAP service includes major biological databases and applications demonstrating a simple method of implementing WAP interfaces to uncompliant applications, i.e. the applications that are not WAP or Internet based. The BioWAP service can be browsed with any WAP terminal.     

Analytical quality control program used by the trace elements in foods and diets sub-network of the FAO European cooperative network on trace elements

Summary The analytical quality control program employed by the ongoing FAO study on 14 trace elements in nationally representative staple foods of European countries is presented. The analytical quality control used is based on: 1) precautions taken to avoid trace element contaminations or losses during sampling and sample handling; and, 2) on methods used to guarantee that the actual determinations yield correct results. The precautions are presented. A number of certified biological reference materials (RMs) were used to validate the analytical methods employed. The following staple food RMs were also prepared: wheat flour, potato powder, animal muscle (pork) and milk powder. They were tested for homogeneity and subjected to an interlaboratory comparison study on the basis of which recommended values for trace element concentrations were defined. Further, the mean relative standard deviation for the 95% confidence limits of the medians in all RMs was below 5% for Ca, Mg and Zn; below 10% for Mn; below 15% for Fe, Cu and Se; and below 25% for Mo and Ni. These RMs were used to control the analytical quality of the trace element determinations in the actual samples. It is concluded that important contaminations were avoided in sampling and sample handling and that use of the RMs described was necessary to guarantee the analytical quality of the results.     

Improving eigenvalue bounds using extra bounds

Bounds for various functions of the eigenvalues of a Hermitian matrix A, based on the traces of A and A², are improved. A technique is presented whereby these bounds can be improved by combining them with other bounds. In particular, the diagonal of A, in conjunction with majorization, is used to improve the bounds. These bounds all require O(n²) multiplications.     

A Novel Intramolecular Cyclization Reaction: Facile Solvent-Free Microscale Synthesis Suitable for Rapid Production of Libraries of 3-Amino-1,2,4-Triazines and for Combinatorial Chemistry

A novel intramolecular cyclization reaction is reported, in which various 1,2-bis(amidinohydrazone)s are converted into 3-amino-1,2,4-triazine or its substituted analogues. The reaction is easily carried out at microscale as well as ordinary scale level by heating the appropriate bis(amidinohydrazone) to roughly 200°C in an inert atmosphere or in vacuo. No solvents or other reagents are needed. The products are easily isolated, being sublimed off from the starting material and forming single crystals. A microscale procedure employing glass ampoules as the reaction vessel is described. The reaction is rapid and offers a facile way of preparing large series of substituted 3-amino-1,2,4-triazines individually in crystalline form for screening purposes. Because large numbers of bis(amidinohydrazone)s have been synthesized for biochemistry and drug development and libraries exist, the present method may be more practical than combinatorial approaches for the production of 3-amino-1,2,4-triazines, as it allows simultaneous individual syntheses. As the reaction is intramolecular, it is probable that the method can also be used also for mixtures of bis(amidinohydrazone)s to produce several triazines in one ampoule. The structure of the products was confirmed by mass, NMR and IR spectroscopy, elemental analyses and comparison with authentic samples. The reaction was studied using five bis(amidinohydrazone)s of aliphatic glyoxals, phenylglyoxal bis(amidinohydrazone) as well as the bis(amidinohydrazone) of 1,2-cyclohexanedione as starting materials. From the compound mentioned last a bicyclic product was obtained. In the case of the unsymmetric starting material ethylglyoxal bis(amidinohydrazone), both possible isomers were formed. The safety of heating the nitrogen-rich starting materials in large-scale syntheses has not been verified.